I. Field of the Invention
The present invention relates to wireless telecommunications. More particularly, the present invention relates to a novel and improved method and apparatus for supporting signaling data transmission in an adjustable rate wireless communication system.
II. Description of the Related Art
FIG. 1 is a highly simplified illustration of a cellular telephone system configured in accordance with the use of digital signal processing techniques. To conduct a telephone call or other communication, a wireless interface is established between a subscriber unit 18 and one or more base stations 12 using digitally modulated radio frequency (RF) signals. Each wireless interface is comprised of a forward link transmission from the base station 12 to the subscriber unit 18 and a reverse link transmission from the subscriber unit 18 to the base station 12. Typically, one or more channels are established within the forward and reverse link transmission which include a forward traffic channel and a reverse traffic channel over which the user data such as voice or digital data is transmitted. Using one or more wireless interfaces, a subscriber unit 18 communicates with other systems by way of mobile telephone switching office (MTSO) 10, including public switched telephone network (PSTN) 19, and any other systems coupled thereto. Typically, MTSO 10 is coupled to PSTN 19 and to base stations 12 via wire line links including, for example, T1 or E1 links, the use of which is well known in the art.
In addition to digitized voice and other digitized user data, cellular telephone systems must transmit signaling data via the wireless link. Signaling data is used to control and exchange information between the various subsystems that make up the cellular telephone network. The transmission of signaling data via the wireless link is typically performed by establishing a second set of channels in the forward and reverse link transmissions specifically designated for the transmission of signaling data over the wireless link, or by multiplexing the signaling data onto the traffic channels while temporarily reducing or suspending the transmission of the user data. In many instances, multiplexing the user data and signaling data over a single traffic channel is preferred because processing a single channel at the receive system is less complex than processing a set of channels. Various systems and methods for transmitting user data and signaling data via single traffic channel are disclosed in pending U.S. patent applications Ser. No. 08/171,146 entitled "METHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION", now U.S. Pat. No. 5,504,773, Ser. No. 08/374,444 entitled "METHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION", now U.S. Pat. No. 5,568,473, as well as issued patents U.S. Pat. No. 5,103,459 entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM" and U.S. Pat. No. 4,901,307 entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS" each of which is assigned to the assignee of the present invention.
Since the initial development of many digital cellular telecommunications systems, the need for higher data rate wireless telecommunication systems has developed, as well as for wireless telecommunication systems that operate at a greater variety of data rates. Additionally, some new wireless applications require that a constant user data transmission rate be provided. In the context of these new applications, temporarily reducing or suspending the transmission of user data to allow signaling data to be transmitted is not feasible. Therefore, to satisfy these new requirements the present invention is directed to providing wireless telecommunication capability at a wide variety of transmission rates without the need to reduce the user data transmission rate in order to send signaling data. Additionally, to avoid increased complexity, the present invention is directed to providing this capability via the use of a single traffic channel.